The present invention relates to a new and improved method of making of compound x-ray lenses and a new and improved variable focus x-ray lens assembly.
X-ray lenses are used to focus x-ray beams produced, for example, with synchrotron and lab-based x-ray sources. X-ray beams can be focused by a variety of mechanisms including mirror, crystals, zone plates, and capillaries. However, since the real part of the index of refraction decrement of materials for x-rays is very, very small, and negative, (xcx9c xe2x88x9210xe2x88x928 to xe2x88x9210xe2x88x926) it is necessary, respectively, to use several aligned lenses to affect significant x-ray focusing, and x-ray focusing generally requires concave rather than convex-shaped lenses.
A variety of methods for the fabrication of an x-ray focusing lens system composed of several double-sided concave lenses have been suggested. If one-dimensional focusing is sought, then a substrate with a number of aligned cylindrical holes drilled into it can be used. Presently, cylindrical holes of circular cross-section are used for one-dimensional x-ray focusing because they are easy to make. To reduce spherical aberrations in x-ray focusing, it is better to use parabolic-shaped cylinders, rather than circular. Normal drilling cannot produce non-circular-shaped cylinders. If two-dimensional focusing is desired, then spherical or paraboloidal cavities must be configured.
A principal object of the present invention is to provide a new and improved method of making x-ray lenses and a new variable focus x-ray lens assembly.
It is another object of the invention to provide such method of making x-ray lenses and variable focus x-ray lens assembly that requires no or minimal alignment of individual lenses, has substantially smooth walls, has minimal x-ray absorption, and that is easy and economical to manufacture.
It is another object of the invention to provide such method of making x-ray lenses and variable focus x-ray lens assembly that facilitates forming the x-ray lenses of different materials, the x-ray lenses having arbitrary lens profiles, and the use of an arbitrary number of x-ray lenses for variable focusing.
It is another object of the invention to provide method of making x-ray lenses and variable focus x-ray lens assembly substantially without negative effect and that overcome many of the disadvantages of prior arrangements.
In brief, a method for producing microstructures for use for x-ray lenses using extrusion techniques and a variable focus x-ray lens assembly are provided. An elongated strip containing a series of aligned cylindrical compound x-ray lenses is formed by extrusion. A predefined lens profile of the cylindrical compound x-ray lenses has, for example, a parabolic profile for x-ray focusing.
In accordance with the invention, the elongated strip contains a series of aligned x-ray lenses formed of selected metals, plastics, ceramics and compounds and produced by an extrusion step. For focusing low to moderate energy x-rays, materials having low atomic numbers are used. The elongated strip of multiple cylindrical x-ray lenses can be cut into multiple, generally uniform small lengths, and positioned within a support member. Cutting the assembled support member and x-ray lenses at a selected angle provides a variable focus x-ray lens assembly.